Question

我写了一个多线程模拟退火程序，但它没有运行。我不确定代码是否正确。代码能够编译但是当我运行代码时它会崩溃。它只是一个运行时错误。

#include <stdio.h> 
#include <time.h>
#include <iostream>
#include <stdlib.h>
#include <math.h>
#include <string>
#include <vector>
#include <algorithm>
#include <fstream>
#include <ctime>
#include <windows.h>
#include <process.h> 

using namespace std;



typedef vector<double> Layer; //defines a vector type

typedef struct {
   Layer Solution1;
   double temp1;
   double coolingrate1;
   int MCL1;
   int prob1;
}t; 
//void SA(Layer Solution, double temp, double coolingrate, int MCL, int prob){


double  Rand_NormalDistri(double mean, double stddev) {
 //Random Number from Normal Distribution

    static double n2 = 0.0;
    static int n2_cached = 0;
    if (!n2_cached) {
       // choose a point x,y in the unit circle uniformly at random
     double x, y, r;
     do {
  //  scale two random integers to doubles between -1 and 1
   x = 2.0*rand()/RAND_MAX - 1;
   y = 2.0*rand()/RAND_MAX - 1;

    r = x*x + y*y;
   } while (r == 0.0 || r > 1.0);

        {
       // Apply Box-Muller transform on x, y
        double d = sqrt(-2.0*log(r)/r);
      double n1 = x*d;
      n2 = y*d;

       // scale and translate to get desired mean and standard deviation

      double result = n1*stddev + mean;

        n2_cached = 1;
        return result;
        }
    } else {
        n2_cached = 0;
        return n2*stddev + mean;
    }
}



double   FitnessFunc(Layer x, int ProbNum)
{


    int i,j,k;
    double z; 
  double fit = 0;  
  double   sumSCH; 

 if(ProbNum==1){
  // Ellipsoidal function
  for(j=0;j< x.size();j++)
    fit+=((j+1)*(x[j]*x[j]));
}

 else if(ProbNum==2){
  // Schwefel's function
  for(j=0; j< x.size(); j++)
    {
      sumSCH=0;

      for(i=0; i<j; i++)
    sumSCH += x[i];
      fit += sumSCH * sumSCH;
    }
}

 else if(ProbNum==3){
  // Rosenbrock's function

  for(j=0; j< x.size()-1; j++)
    fit += 100.0*(x[j]*x[j] - x[j+1])*(x[j]*x[j] - x[j+1]) + (x[j]-1.0)*(x[j]-1.0);
}
  return fit;
}

double probl(double energychange, double temp){
    double a;
    a= (-energychange)/temp;
    return double(min(1.0,exp(a)));
}

int random (int min, int max){
    int n = max - min + 1;
    int remainder = RAND_MAX % n;
    int x;
    do{
        x = rand();
    }while (x >= RAND_MAX - remainder);
    return min + x % n;
}

//void SA(Layer Solution, double temp, double coolingrate, int MCL, int prob){
void SA(void *param){

    t *args = (t*) param;

    Layer Solution = args->Solution1;
    double temp = args->temp1;
    double coolingrate = args->coolingrate1;
    int MCL = args->MCL1;
    int prob = args->prob1;

    double Energy;
    double EnergyNew;
    double EnergyChange;
    Layer SolutionNew(50);

    Energy = FitnessFunc(Solution, prob);

    while (temp > 0.01){

        for ( int i = 0; i < MCL; i++){
            for (int j = 0 ; j < SolutionNew.size(); j++){

                SolutionNew[j] = Rand_NormalDistri(5, 1);
            }
            EnergyNew = FitnessFunc(SolutionNew, prob);
            EnergyChange = EnergyNew - Energy;

            if(EnergyChange <= 0){
                Solution = SolutionNew;
                 Energy = EnergyNew;    
            }
            if(probl(EnergyChange ,temp ) >  random(0,1)){
                //cout<<SolutionNew[i]<<endl;
                Solution = SolutionNew;
                 Energy = EnergyNew;
                cout << temp << "=" << Energy << endl;
            }
        }
        temp = temp * coolingrate;
    }

}




int main ()
{ 

 srand ( time(NULL) ); //seed for getting different numbers each time the prog is run


Layer SearchSpace(50); //declare a vector of 20 dimensions

//for(int a = 0;a < 10; a++){

for (int i = 0 ; i < SearchSpace.size(); i++){

    SearchSpace[i] = Rand_NormalDistri(5, 1);
}

t *arg1;
arg1 = (t *)malloc(sizeof(t));
arg1->Solution1 = SearchSpace;
arg1->temp1 = 1000;
arg1->coolingrate1 = 0.01;
arg1->MCL1 = 100;
arg1->prob1 = 3;

//cout << "Test " << ""<<endl;
_beginthread( SA, 0, (void*) arg1);
Sleep( 100 );

//SA(SearchSpace, 1000, 0.01, 100, 3);
//}

  return 0;
}

请帮忙。

由于 Avinesh

Answer 1

虽然我不知道你崩溃的真正原因但我并不感到惊讶你最终遇到了麻烦。例如，Rand_NormalDistri中的那些“缓存”静态变量显然容易受到数据竞争的影响。你为什么不用std::normal_distribution？在标准库例程可用时使用标准库例程几乎总是一个好主意，当你需要考虑多线程技巧时更是如此。

更糟糕的是，你正在大量混合使用C和C ++。 malloc是您在C ++代码中几乎从不使用的东西 - 它不知道RAII，它是您可以在C ++中使用的少数本质安全的东西之一。

Answer 2

正如左边所指出的那样，你在C ++代码中使用了malloc。这是你崩溃的根源。

Malloc将分配一块内存，但由于它实际上是为C设计的，因此它不会调用任何C ++构造函数。在这种情况下，矢量＆lt; double＆gt;从来没有正确构建。当

arg1->Solution1 = SearchSpace;

调用时，成员变量“Solution1”具有未定义状态，并且赋值运算符崩溃。

而不是malloc试试

arg1 = new t;

这将完成大致相同的事情，但“new”关键字也会调用任何必要的构造函数来确保向量＆lt; double＆gt;已正确初始化。

这也带来了另一个小问题，你新建的内存也需要在某处删除。在这种情况下，由于arg1被传递给另一个线程，它应该被清理，如

delete args;

完成args变量之后，通过“SA”函数

。

多线程模拟退火

2 个答案: